As an electromagnetic contactor used in a high-current direct current power circuit, heretofore, there has been proposed a plunger type electromagnetic contactor including a housing 500 housing a pair of fixed contacts 501, 502 disposed to maintain a predetermined interval, a movable contact bearing body 505 including at the two respective ends thereof a pair of movable contacts 503, 504 disposed to face the pair of fixed contacts 501, 502 so as to be capable of contacting to and separating from the pair of fixed contacts 501, 502, and a pair of arc extinguishing means 506, 507 for extinguishing arcs generated in each of the contact gaps between the pair of fixed contacts 501, 502 and the pair of movable contacts 503, 504, as shown in FIGS. 12 and 13 (for example, refer to PTL 1).
Herein, each of the pair of arc extinguishing means 506, 507 is configured of a pair of permanent magnets fixed in the housing so that the magnetic pole faces facing each other across the contact gap have opposite polarities.
A description of an arc extinguishing principle of the heretofore known example described above will be given using FIGS. 13 to 16. As shown in FIG. 13, when the movable contact bearing body 505 is moved from an energized state wherein current flows from the fixed contact 501 through the movable contacts 503, 504 toward the fixed contact 502 by contacting the movable contacts 503, 504 to the fixed contacts 501, 502, by a solenoid portion not shown in the drawing in a direction in which the movable contacts 503, 504 move upward away from the fixed contacts 501, 502, and placed in a state in which the current is interrupted, arcs 508 are generated between each fixed contact 501, 502 and each respective movable contact 503, 504, as shown in FIG. 14.
At this time, as the pair of arc extinguishing means 506, 507 is disposed in a direction perpendicular to the arcs 508, and as shown in FIG. 15, magnetic fluxes φ therefrom are generated in a direction perpendicular to the plane of the drawing, Lorentz forces that direct the arcs 508 outward in the array direction of the fixed contacts 501, 502 in accordance with Fleming's left-hand rule act on the magnetic fluxes φ and the direction of current, and the arcs are extended to the side of an arc extinguishing space 509 disposed on the outer side in the array direction of the fixed contacts 501, 502 shown in FIG. 15, and are extinguished.
Also, when the direction in which the current is conducted is opposite to a direction in which the current flows from the fixed contact 502 to the fixed contact 501 side via the movable contacts 504, 503, arcs generated between each fixed contact 501, 502 and each respective movable contact 503, 504 are extended inward in the array direction of the fixed contacts 501, 502, and are extinguished, as shown in FIG. 16.
However, in the heretofore known example described in the PTL 1, the current is interrupted by the arcs being extended to make an arc voltage higher than a power supply voltage. As the arc voltage is determined by the product of an arc electric field value and arc length, it is necessary to increase the arc electric field value or increase the arc length when intending to interrupt a higher power supply voltage.
An arc electric field value in the atmosphere has been determined by the internal pressure and gas species, and it is possible to increase an arc electric field, in general, by increasing the pressure of gas, or by using, for example, a gas such as hydrogen with a large arc electric field. However, there is an unsolved problem that it is necessary to tightly seal a receptacle or increase the strength of structure when the pressure of gas is high. Also, as the dielectric strength voltage deteriorates when using a gas such as hydrogen with a large arc electric field, it is necessary to increase the gap between the contacts, there is an unsolved problem such as the coil of the solenoid portion that drives the movable contact bearing body so as to cause the movable contact bearing body to advance and withdraw is large.
Meanwhile, when increasing the arc length, it is necessary to provide an arc space large enough to achieve the arc length, and there is an unsolved problem that the housing becomes larger.
In order to solve these unsolved problems, there is proposed an electromagnetic relay wherein arc extinguishing magnetic bodies are disposed on each outer side in the array direction of the fixed contacts so that the opposing faces thereof are different poles, and arc extinguishing spaces for extending arcs with Lorentz forces based on the magnetic fluxes of the arc extinguishing magnetic bodies are disposed at each end of the arc extinguishing magnetic bodies in a direction perpendicular to the array direction of the fixed contacts and perpendicular to the switching direction of the fixed contacts and movable contacts (for example, refer to PTL 2).